1. Field of the Invention
This invention relates generally to internally heated rollers, and more particularly to a coupling for securely mounting a gudgeon in driving engagement with an internally heated roller.
2. Description of the Prior Art
In the printing and paper making industries, internally heated rollers are commonly used to feed paper sheets and simultaneously perform some processing step on the paper. For example, an internally heated roller may serve as a pressure roll fuser for electrographic copiers, or as a calender in making paper. In such applications, the roller is supported on gudgeons and is rotated by a drive mechanism connected to the roller through the gudgeons. Heat through the surface of the roller accomplishes the desired fixing of toned images to the sheets or calendering of the paper. In order to decrease heat losses through the ends of the roller to the surrounding environment, the gudgeons on the end of the roller are generally constructed of a material having a relatively low thermal conductivity (e.g. plastic). However, such materials generally do not match the physical characteristics of the roller (e.g. metal) in, for example, strength, stiffness or rate of thermal expansion. Thus, it is difficult to maintain the drive connection between the internally heated roller and its end gudgeons.
Volume 130, page 23, of the Research Disclosure Bulletin, published in Hampshire, United Kingdom, shows several configurations of internally heated rollers and their end gudgeons. These configurations are intended to minimize the effect of different physical characteristics so that the gudgeons support and drive an associated roller over extended temperature ranges without loosening, becoming relatively eccentric, or inducing excessive stresses in the roller. In each of the depicted configurations bolts are used to secure the gudgeons to the roller. While such configurations do improve operating characteristics, repetitive heating and cooling of the roller frequently cause the bolts to relax the coupling between the gudgeon and roller or ultimately to fracture.